This invention relates generally to a trocar seal which prevents loss of gas pressure when an instrument is inserted through, or withdrawn from, the seal. More specifically, it relates to a flexible, elastomeric seal especially suited for use with surgical instruments necessary for numerous laparoscopic procedures.
Sealing devices for trocar assemblies are an important aspect of the design of instruments used in laparoscopic surgical procedures. A laparoscopic surgical procedure utilizes several small puncture openings, mainly in the abdominal wall, to allow insertion of specialized surgical instruments instead of one large incision in a traditional open surgical procedure. The laparoscopic procedure is becoming widely accepted because of its many advantages such as: less trauma to the patient, shorter recovery time, reduced adhesions, and less post operative pain. The laparoscopic surgical technique requires inflation of the abdominal cavity to lift the abdominal wall from the internal organs to create working space for the surgeon and to introduce light generating and optical viewing instruments.
During the laparoscopic surgical procedure, the internal gas pressure must be maintained in order to successfully complete the procedure. In order to maintain the internal gas pressure while instruments are passed into and out of the openings in the abdominal cavity, sealing devices are required for both the instruments and for the trocar assemblies used to make and maintain the small openings. In a trocar assembly, the obturator punctures the pressurized abdomen. The obturator generally slides within the cannula of the trocar assembly, which is the hollow tube portion of the trocar which remains in the abdominal wall after puncturing.
During the laparoscopic procedure, it is desirable to seal the cannula from loss of internal gas pressure. The seal functions while the obturator pierces the abdominal wall, after the obturator is withdrawn, and while other instruments are inserted through the cannula. Additionally, it is desirable that the seal produce a small amount of resistance to the insertion force by surgical instruments passing through the trocar cannula. Furthermore, it is desirable that the seal maintain gas pressure in the abdominal cavity, despite numerous insertions and withdrawals of surgical instruments through the trocar cannula.
Current sealing devices for laparoscopic instruments are typified by numerous designs. For example, one design includes a spring loaded valve in combination with a sealing gasket to conform to the cross section of the surgical instrument inserted through the trocar cannula. This two part valve assembly performs adequately as a seal but may be more complex than truly desired. U.S. Pat. No. 5,141,498 shows at least three flexible leaflets, and U.S. Pat. No. 4,424,833 shows a sponge type seal with three connecting slits.
Multiple leaflet and multiple slit devices may seal well when a surgical instrument is not inserted through them but will tend to create gaps around inserted instruments having circular cross sections and will also tend to cause eversion of their sealing surfaces when the instruments are withdrawn. Eversion of the sealing surfaces is likely to cause gaps between the sealing surfaces resulting in gas leakage through the seal. U.S. Pat. No. 5,242,412 shows a duck bill valve design applied to a trocar device. This design provides a straight single slit to seal against a surgical instrument. U.S. Pat. Nos. 4,475,548; 4,809,679; and 4,143,853 show single slit designs also. A single slit seal is also subject to a lack of conforming to circular shapes and to eversion upon withdrawal of surgical instruments.
A study of these references indicates a need for a simpler one piece seal for use in trocars to seal against gas pressure during a laparoscopic surgical procedure. In addition, it is desirable to have a one piece assembly with a simple design which would not require an excessive force to insert an instrument through it and would resist eversion of the sealing edges once the surgical instrument is withdrawn.